To save: right-click (Windows) or control-click (Mac) on the image and select "Save image."

Allopatric speciation

Image caption:In this mode of speciation, something extrinsic to the organisms prevents two or more groups from mating with each other regularly, eventually causing that lineage to speciate. Isolation might occur because of great distance or a physical barrier, such as a desert or river.

Image credit:
If you use this image in your own non-commercial project please credit it to the University of California Museum of Paleontology's Understanding Evolution (http://evolution.berkeley.edu).